Evidence for an influence of CSF sodium concentration upon ACTH-mediated cortisol response to intravenous and intracerebroventricular angiotensin II.

The influence of cerebrospinal fluid (CSF) NaCl concentration upon the cortisol release induced by intracerebroventricular (i.c.v.) and intravenous (i.v.) infusions of angiotensin II (AII) was studied in conscious goats. A first series of experiments involved i.c.v. infusion (20 min; 20 microliters min-1) of simply hypertonic (0.5 M) NaCl, or of AII (2 pmol kg-1 min-1) dissolved in 0.5 M or isotonic (0.15 M) NaCl or in isotonic glucose. The most pronounced rise in plasma cortisol concentration (PC) was elicited by AII in 0.5 M NaCl, but responses of nearly the same size were obtained by merely 0.5 M NaCl and by AII in isotonic NaCl, whereas AII in glucose induced a smaller PC rise. An urge to drink developed during all infusions, except during the AII/glucose infusion. Here, however, thirst became apparent 2-6 min post-infusion. When, in a second series, the hypertonicity of the NaCl was reduced to 0.3 M, and the dose of AII to 0.5 pmol kg-1 min-1, only the infusion of AII in 0.3 M NaCl elicited any appreciable rise in PC. The response was approximately the same size as that earlier obtained as the effect of the larger dose of AII dissolved in isotonic saline. In a third series of experiments, a 30-min i.c.v. infusion of isotonic glucose, preceding and out-lasting a 10-min i.v. infusion of AII (40 pmol kg-1 min-1), was found to extinguish the rise in PC obtained as the effect of a separate i.v. infusion of AII.(ABSTRACT TRUNCATED AT 250 WORDS)